Experiments in this proposal are designed to determine if Rho proteins regulate morphogenic movements during Xenopus gastrulation. The preliminary results presented suggest that RhoA regulates a specific cell movement which occurs during gastrulation, convergent-extension movements. Experiments proposed in Specific Aim number 1 will further investigate this possibility by determining if convergent-extension movements of endogenous mesoderm in vitro require Rho protein function. Experiments in Specific Aim number 2 will determine if Rho kinases, which links RhoA to regulation of the actin cytoskeleton, mediate convergent-extension movements during gastrulation. Finally, experiments in Specific Aim number 3 are design to isolate Xenopus RhoA homologues and determine if they mediate convergent-extension movements during gastrulation. These experiments are important to human health because of the role that Rho proteins play in cell movements in human disease. Rho proteins and Rho kinase have been shown to play a pivotal role in tumor formation, metatasis and in hypertension. Therefore, a study of the in vivo role of these molecules during development may provide further clues as to how their activity may be regulated in these diseases.